<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>这就是我的第一个网页</title>
    <style>
        h1 {
            background-color: aqua;
        }

        hr {
            border: 1px solid rgb(0, 0, 0);
        }
    </style>
</head>

<body>
    <h1>Hello&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;World!</h1>
    <h2>你好，世界！</h2>
    <h3>你好，世界！</h3>
    <h4>你好，世界！</h4>
    <h5>你好，世界！</h5>
    <h6>你好，世界！</h6>
    <hr>
    <div><strong>加粗</strong></div>
    <B>加粗</B><br>
    <div><em>斜体</em></div>
    <i>斜体</i><br>
    <ins>下划线</ins><br>
    <u>下划线</u>
    <div><s>删除线</s></div>
    <div><del>删除线</del></div>
    &lt;h1&gt;&lt;/h1&gt;
</body>

</html>